Gonorrhea is a type III legal communicable disease caused by Neisseria gonorrhoeae (NG), one of the most common sexually transmitted bacteria worldwide. NG infection can cause urethritis or systemic inflammation and may lead to infertility or other complications. The NACHT, LRR, and PYD domains-containing protein 3 (NLRP3) inflammasome is a protein complex composed of NLRP3, apoptosis-associated speck-like protein and caspase-1 and is an important part of the cellular machinery controlling the release of interleukin (IL)-1β and IL-18 and the pathogenesis of numerous infectious diseases. It has been reported that NG infection activates the NLRP3 inflammasome; however, the underlying mechanism remain unclear. In this report, the signaling pathways involved in the regulation of NG-mediated NLRP3 inflammasome activation in macrophages were studied. The results indicated that viable NG, but not heat-killed or freeze/thaw-killed NG, activated the NLRP3 inflammasome in macrophages through toll-like receptor 2, but not toll-like receptor 4. NG infection provided the priming signal to the NLRP3 inflammasome that induced the expression of NLRP3 and IL-1β precursor through the nuclear factor kappa B and mitogen-activated protein kinase pathways. In addition, NG infection provided the activation signal to the NLRP3 inflammasome that activated caspase-1 through P 2 X 7 receptor-dependent potassium efflux, lysosomal acidification, mitochondrial dysfunction, and reactive oxygen species production pathways. Furthermore, we demonstrated that NLRP3 knockout increased phagocytosis of bacteria by macrophages and increases the bactericidal activity of macrophages against NG. These findings provide potential molecular targets for the development of anti-inflammatory drugs that could ameliorate NG-mediated inflammation.

Gouty arthritis results from the generation of uric acid crystals within the joints. These uric acid crystals activate the NACHT, LRR and PYD domains-containing protein 3 (NLRP3) inflammasome, which is involved in chronic inflammatory diseases, including gouty arthritis. This study identified the polyenylpyrrole derivative 4-hydroxy auxarconjugatin B (4-HAB), a novel autophagy inducer, which attenuated uric acid crystals-mediated activation of the NLRP3 inflammasome in vitro and in vivo. 4-HAB dose-dependently reduced the release of interleukin (IL)-1β, IL-18, active caspase-1 and apoptosis-associated speck-like protein (ASC) in uric acid crystals-activated macrophages. In a mechanistic study, 4-HAB was shown to inhibit uric acid crystals-induced mitochondrial damage, lysosomal rupture and ASC oligomerization. Additionally, 4-HAB inhibited the NLRP3 inflammasome through Sirt1-dependent autophagy induction. Furthermore, the anti-inflammatory properties of 4-HAB were confirmed in a mouse model of uric acid crystals-mediated peritonitis by the reduced levels of neutrophil influx, IL-1β, active caspase-1, IL-6 and MCP-1 in lavage fluids. In conclusion, 4-HAB attenuates gouty inflammation, in part by attenuating activation of the NLRP3 inflammasome through the Sirt1/autophagy induction pathway.

Shigella is one of the leading bacterial causes of diarrhea worldwide, affecting more than 165 million people annually. Among the serotypes of Shigella, Shigella sonnei is physiologically unique and endemic in human immunodeficiency virus-infected men who have sex with men. The NOD-, LRR-, and pyrin domain-containing protein 3 (NLRP3) inflammasome, a protein complex composed of NLRP3, apoptosis-associated speck-like protein, and caspase-1, recognizes, and responds to pathogen infection and diverse sterile host-derived or environmental danger signals to induce IL-1β and IL-18 production. Although the Shigella flexneri-mediated activation of the NLRP3 inflammasome has been reported, the effect of S. sonnei on NLRP3 inflammasome activation remains unclear. We found that S. sonnei induced IL-1β production through NLRP3-dependent pathways in lipopolysaccharide-primed macrophages. A mechanistic study revealed that S. sonnei induced IL-1β production through P 2 X 7 receptor-mediated potassium efflux, reactive oxygen species generation, lysosomal acidification, and mitochondrial damage. In addition, the phagocytosis of viable S. sonnei was important for IL-1β production. Furthermore, we demonstrated that NLRP3 negatively regulated phagocytosis and the bactericidal activity of macrophages against S. sonnei. These findings provide mechanistic insight into the activation of the NLRP3 inflammasome by S. sonnei in macrophages.

IgA nephropathy (IgAN), an immune complex‐mediated process and the most common primary glomerulonephritis, can progress to end‐stage renal disease in up to 40% of patients. Accordingly, a therapeutic strategy targeting a specific molecular pathway is urgently warranted. Aided by structure characterisation and target identification, we predicted that a novel ring‐fused 6‐(2,4‐difluorophenyl)‐3‐(3‐(trifluoromethyl)phenyl)‐2H‐benzo[e][1,3]oxazine‐2,4(3H)‐dione (LCC18) targets the NLRP3 inflammasome, which participates in IgAN pathogenesis. We further developed biomarkers for the disease. We used two complementary IgAN models in C57BL/6 mice, involving TEPC‐15 hybridoma‐derived IgA, and in gddY mice. Moreover, we created specific cell models to validate therapeutic effects of LCC18 on IgAN and to explain its underlying mechanisms. IgAN mice benefited significantly from treatment with LCC18, showing dramatically improved renal function, including greatly reduced proteinuria and renal pathology. Mechanistic studies showed that the mode of action specifically involved: (1) blocking of the MAPKs/COX‐2 axis‐mediated priming of the NLRP3 inflammasome; (2) inhibition of ASC oligomerisation and NLRP3 inflammasome assembly by inhibiting NLRP3 binding to PKR, NEK7 and ASC; and (3) activation of autophagy. LCC18 exerts therapeutic effects on murine IgAN by differentially regulating NLRP3 inflammasome activation and autophagy induction, suggesting this new compound as a promising drug candidate to treat IgAN. © 2020 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.